Saturday, 8 April 2017

statistics - The three-coin-flip riddle

Is the following true (It seems obvious to me that it's not... but... a PhD in physics, Derek Abbott, seems to think others explanation at end of post):



Someone flips 3 coins on the table, they are then covered with paper so I can't see. Two of the coins are on the left of the table, one coin is on the right of the table. I go to the left of the table and start to slide the paper back slowly, eventually revealing the first of the two coins, if it's tails I just have the person re-flip, but if it's heads then I predict the other coin is tails and continue pulling the paper back to reveal tails 66% of the time.






Ted-ed (a TED talks division) published a video recently via Physics PHD Derek Abbott called "The Frog Riddle" - you can watch it here: https://www.youtube.com/watch?v=cpwSGsb-rTs and now I'm very confused, please tell me their video is just wrong.




I don't understand mathematically how they are arriving at their conclusion. If this were any other youtube video in my feed I would just wave it off as erroneous, but TED is a very large and very famous organization with lots of editors and is also notoriously intellectual. Also I was having a hard time finding many who disagreed in the youtube comments.

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